Assessment of Fredlund Xing's soil-water characteristic equation for tropical soils

摘要

This paper focuses on a study relative to the utilization of the equation proposed by Fredlund & Xing (1994) to represent the development of soil-water characteristic curves (SWCC): theta = theta (PSI.a.m.n) from low to medium suction values. The adequateness of such equation was tested with respect to Brazilian typical tropical soils. Soil samples were subjected to compaction and suction tests using the Brazilian MCT-M methodology and a Richards's pressure extractor. Using the obtained laboratory soil suction curves it is possible to estimate the parameters a, m and n in such a way that Fredlund & Xing's equation can be obtained. Then, measured and estimated (PSI,theta) values concerning each particular soil sample are plotted so that practical andtheoretical curves can be compared. This comparison enables one to calculate the relative error (epsilon) between measured and estimated PSI,theta) values in such a manner that a whole analysis concerning the fitness peculiarities of this equation applied to tropical soils is accurately fulfilled.